Continuous ink jet printer print head

Abstract

A print head for a continuous ink jet printer has a nozzle through which ink is emitted and broken up into droplets under the action of a piezoelectric oscillator. A charge electrode applies charge to selected droplets and a deflection electrode deflects the path of the charged droplets to cause printing on a substrate. A gutter collects droplets which are not required for printing. A charge electrode, together with one of the deflection electrodes is movable in a direction transverse to the path of the droplets selectively under the action of pressurized ink fed from an ink supply. Similarly, the gutter is movable in the same way by another actuator.

We claim: 
     
       1. A printhead for a continuous ink jet printer having an ink supply means for supplying ink under pressure to the print head, the print head comprising: at least one nozzle through which said ink under pressure is emitted in use and broken up into droplets;   at least one nozzle charge electrode for applying electrostatic charge to selected droplets in use;   at least one deflection electrode for deflecting a path of the charged selected droplets;   a gutter for collecting said charged selected droplets not required for printing; and   at least one hydraulic actuator coupled to the at least one charge electrode, said ink supply means supplies said ink under pressure from the ink supply means to both said at least one hydraulic actuator and said at least one nozzle;   wherein movement of the at least one movable charge electrode is in a direction transverse to the path of the droplets, and said movement is controlled by said ink under pressure selectively supplied to the at least one actuator.   
     
     
       2. A print head according to claim 1, wherein the at least one deflection electrode is mounted for movement with the at least one charge electrode. 
     
     
       3. A print head according to claim 1, wherein the at least one charge electrode is biased to a non-operating position. 
     
     
       4. A print head according to claim 1, wherein the at least one charge electrode is moved laterally out of said at least one charge electrode's normal operating position so that said at least one charge electrode is withdrawn from proximity to the stream of droplets. 
     
     
       5. A print head according to claim 4, constructed such that, during start-up, the at least one charge electrode is withdrawn from said at least one charge electrode's normal operating position laterally to avoid being spattered by ink droplets. 
     
     
       6. A print head for a continuous ink jet printer having an ink supply means for supplying ink under pressure to the print head the print head comprising: at least one nozzle through which said ink under pressure is emitted in use and broken up into droplets;   at least one charge electrode for applying electrostatic charge to selected droplets in use;   at least one deflection electrode for deflecting a path of the charged selected droplets;   a movable gutter for collecting said charged selected droplets not required for printing; and   at least one hydraulic actuator coupled to the gutter, wherein the ink supply means supplies said ink under pressure to said at least one hydraulic actuator;   wherein movement of the movable gutter is in a direction transverse to the path of the droplets, and said movement is controlled by said ink under pressure selectively supplied to the at least tone actuator.   
     
     
       7. A print head according to claim 6, wherein the gutter is biased to a non-operating position. 
     
     
       8. A print head according to claim 6, wherein the gutter is positioned so that all droplets issuing from the nozzle, whether charged or not, pass into the gutter.